Flexible metallic tube



Dec. 26, 1933. M. MGR@ 1,941,151

Patented Dec. 26, 1933 UNITED STATES vPATENT OFFICE FLEXIBLE METALLIC TUBE Application June 23, 1930. serial No. 463,106

1 Claim.

The present invention relates Yto flexible metallic tubes of the type formed by Winding convolutions of wire upon each other in interlocking relation, such tubes being commonly employed as protective casings for various purposes and also as conduits for the conveyance of fluids, such as lubricants. The object of the invention is to provide an improved flexible metallic tube that will possess greater tensile strength than tubes of the same weight heretofore produced. In addition, the tube is so formed that the extremities of a length of the same may be quickly and rmly attached to terminals of any desiredl form, without the use of solder, or other fastening devices,

- commonly used in connection with such tubes.

The labove and other advantageous features of the invention will hereinafter more fully appear with reference to the accompanying drawing in whichl v Fig. 1 is a plan view of a portion of a completed tube embodying my invention and showing the manner in which the tube is formed.

Fig. 2 is a longitudinal sectional View of a portion of the completed tube shown in Fig. 1.

Fig. 3 is a fragmentary sectional View illustrating the manner in which a terminal is attached'to one end of the tube shown in Fig. 1.

Like reference characters refer to like parts` throughout the drawing.4 Y

Referring to the drawing, the tube is formed by forcibly feedingV a pair of wires 1 and 2 and coiling the. same into a helix upon a suitable mandrel 3. ing the wires 1 and 2 and for coiling them simultaneously on a mandrel 3 is not shown, since mechanism of this type is well known in the art and forms no part of the present invention. The wires 1 and 2 are preferably halfround'in section so that when they are coiled upon the Vmandrel 3, the inside of the tube will present a smooth unbroken surface, as shown in Fig..2. After a number of convolutions of the wires 1 and 2 have been coiled on the mandrel 3, a third wire 4 is fed to the tube being formed, at a distance from the wires 1 and 2, and this wire 4 is wound around the outside of the tube rformed by the wires 1 and 2. The outerwire 4 is triangular in cross section and in the coiling operation, the wire 4 is forced between the convolutions of the double inner coil while it is still bearing on the mandrel 3. Consequently, the wedgelike form of the wire 4 tends to spread apart the convolutions of the inner coil kand keep them un der tension. Since a double coil is formedby the wires 1 and 2, obviously the wire 4 will enter only one of the two continuous grooves between convolutions of the inner double coil, so that the completed tube presents on its outer surface an open helical groove indicated at 5, in the left hand portion of Fig. 1.

The particular mechanism for feed- As shown in Fig-3, this helical vgroove 5 extending aroundy the outer surface of the tube provides a convenient way for attaching terminal members to the end portions of a length Yof tube. One form of terminal which can be conveniently applied to the tube consists of a cylindrical sleeve 6 providingv an internal rib or thread 7 of spiral form, which thread 'l fits within the groove 5 so as to permit thesleeve 6 to be screwed onto the end portion of the completed tube. If desired, the thread '7 may be made somewhat tapering towards one end so that the sleeve 6 will become tightly jammed on the tube after it has been screwed several turns. Obviously, whensleeves 6 have been screwed onto the ends of a length of tube they will hold tightly so that the ends of the tube may be conveniently secured to members which it is desired to mechanically connect, or between which it is desired to transmit fluid, as when using the tube as a flexible conduit. One way of connecting a terminal sleeve 6 to another vmember is byproviding the outer end of the sleeve with standard threads 8 into which may be screwed the thready ed end of a shaft, or pipe 9.

From the foregoing, it is apparent that by the present invention there is provided an improved flexible metallic tube that posessses great tensile strength owing to the provision of the double innerV coil, any pull on the tube being divided between thev wires 1 and 2. InV addition, the tube possesses greater flexibility than one having a single innercoil, since only one of the two continuous grooves between convolutions of the double inner coil is engaged by the wedge shaped wire 4. Furthermore, the provision of an open helicalgroove extending around the outer surface of the tube provides means for firmly attaching, the ends of a length of tube to other members to which it is desired to connect the tube. Lastly, the use of only one outer locking wire for two inner coiled wires, results in a considerable saving in weight of material, without sacrifice of strength, as compared to tubingof the same diameter with a smooth outer surface.

I claim: I

A flexible tube comprising a doubleinner coil providing outer peripheral grooves between the convolutions thereof, said double coil being surrounded by a single outer coil wedgingengagement'with only one of the grooves between the vconvolutions of the inner coil, theouter surface of the completed tube presenting an open groove extending-helically around the entire length of the tube. Y

MICHEL NIGRO. 

